Faculty Bibliography

We describe epicardial ablation using a new device that utilizes 980 nm wavelength laser energy. The device can be used in both open and minimally invasive approaches and should make ablation therapy safe, effective, and easy to use.

As less complex modifications of the Maze procedure have been developed, a number of energy sources have been introduced to facilitate the creation of electrically isolating lesions within the atria. These include cryoablation, radiofrequency, microwave, laser, and focused ultrasound. Although each of these sources works slightly differently, the goal of all thermal sources is to heat tissue to a temperature (50 degrees C) above which irreversible electrical isolation occurs. These sources have been utilized both endocardially in arrested heart procedures as well as epicardially in the beating heart setting. There are several obstacles to the use of these sources epicardially, mostly related to the heat sink effect of endocardial blood. Several recent modifications have been introduced that will hopefully increase the efficacy of these sources in beating heart applications.

Computer (robotic) enhancement has emerged as a facilitator of minimally invasive cardiac surgery and has been used to perform portions of intracardiac procedures via thoracotomy incisions. This report describes the use of the da Vinci surgical system in two totally endoscopic ("closed chest") cardiac operations: atrial septal defect closure and pulmonary vein isolation of atrial fibrillation. ASD closure: Fifteen patients underwent repair of a secundum-type atrial septal defect or patent foramen ovale by a totally endoscopic approach, utilizing the da Vinci robotic system. Cardiopulmonary bypass (CPB) was achieved peripherally. Cardioplegia was administered via the distal port of the arterial cannula after endoballoon inflation. Via three port incisions in the right chest, the entire operation including pericardiotomy; bicaval occlusion; atriotomy; atrial septopexy; and atrial closure was performed by a surgeon seated at a computer console. A fourth 15 mm port was utilized for suction and suture passage by a patient-side assistant. In one case, a recurrent shunt was identified and repaired on POD 5. Median ICU length of stay (LOS) was 20 hours, and median hospital LOS was 4 days. Atrial fibrillation surgery: This report also describes the pathway that we have pursued in the development of a totally endoscopic operation for atrial fibrillation. Beginning with animal models, we tested various ablative energy sources; methods of ablation; and minimally invasive approaches. This work has led to the development of a variety of minimally invasive surgical approaches including a totally endoscopic, robotically assisted beating heart procedure for the treatment of atrial fibrillation.

BACKGROUND: Inhibition of angiotensin-converting enzyme (ACE) predisposes patients to vasodilatory hypotension after cardiopulmonary bypass (CPB). This hypotension has been correlated with arginine vasopressin deficiency and can be corrected by its replacement. In patients receiving ACE inhibition, we investigated whether initiation of vasopressin before CPB would diminish post-CPB hypotension and catecholamine use by avoiding vasopressin deficiency. METHODS: Cardiac surgical patients on ACE inhibitor therapy were randomized to receive vasopressin (0.03 U/min) (n = 13) or an equal volume of normal saline (n = 14) starting 20 minutes before CPB. RESULTS: Vasopressin did not change pre-CPB mean arterial pressure or pulmonary artery pressure. After CPB, the vasopressin group had a lower peak norepinephrine dose than the placebo group (4.6 +/- 2.5 versus 7.3 +/- 3.5 microg/min, p = 0.03), a shorter period on catecholamines (5 +/- 6 versus 11 +/- 7 hours, p = 0.03), fewer hypotensive episodes (1 +/- 1 versus 4 +/- 2, p < 0.01), and a shorter intensive care unit length of stay (1.2 +/- 0.4 versus 2.1 +/- 1.4 days, p = 0.03). CONCLUSIONS: In this cohort, prophylactic administration of vasopressin, at a dose without a vasopressor effect pre-CPB, reduced post-CPB hypotension and vasoconstrictor requirements, and was associated with a shorter intensive care unit stay.

BACKGROUND: Recently, there has been renewed interest in simplifying a surgical cure for atrial fibrillation. Microwave energy ablation provides an easier and faster surgical technique, in lieu of traditional "cut and sew," which can also be applied on the beating heart. METHODS: Specific absorption rate (SAR) and thermal profiles were determined after microwave energy ablation intended for clinical application. Lesion geometry measures obtained in vitro with tissue equivalent media were compared with values collected from animal myocardium. RESULTS: Thermal profile analysis demonstrated lesion penetration depths of 2.5, 3, and 5 mm after 8, 16, and 24 seconds, respectively, with microwave power application of 40 W. Dosimetric studies performed using animal myocardium corresponded to the thermal profile analysis and showed that lesion depth was controlled by the output power and the ablation time. CONCLUSIONS: Lesion geometry in tissue using microwave energy is similar to that predicted from in vitro analysis. The ablation depths and thermal profile of microwave ablation is favorable for performing atrial ablation, and this is corroborated by favorable early clinical results.

Microwave energy is a relatively new energy modality that is being used for surgical atrial ablation as a treatment of atrial fibrillation. Microwave energy works by dielectric heating and has a favorable thermal profile that permits both rapid endocardial and epicardial ablation. The device is also extremely flexible and can be easily adapted to minimally invasive applications. The device has been used in over 600 patients with a success ranging from 70% to 90% and without any device-related complications. Many of these patients have had their ablations performed from the epicardium on the beating heart without the aid of cardiopulmonary bypass. Microwave atrial ablation is likely to become an important part of the surgical armamentarium, particularly for those performing minimally invasive approaches to cure atrial fibrillation.

The purpose of this article is to present and evaluate the various technologies recently developed for the surgical treatment of atrial fibrillation as alternatives or adjuncts to the traditional Maze III procedure and other "cut and sew" techniques. The discussion contains a detailed consideration of the biophysical background of the most common ablation techniques, their mode of tissue injury, the methods of use, and the related complications through a review of the existing literature and analysis of experimental results. All of the current technologies presented are still being tested to augment the success rates and reduce the incidence of complications, although all are not available for clinical use. Radiofrequency and cryoablation have been used clinically on large numbers of patients with varying results. Microwave technology has been used in small groups of patients, and the results are to be evaluated. Laser technology is still in an experimental phase, and the clinical results are forthcoming. True transmurality, reduction of operative time, friendly use of ablation devices, and substantial reduction of complications appear to be the key factors for broad adoption of alternative energy sources for surgical ablation.

BACKGROUND: Patients with prolonged intensive care unit (ICU) stays after cardiac operations are labor intensive and expensive. We sought to determine whether exhaustive ICU efforts result in survival or quality-of-life benefits and whether outcome could be predicted. METHODS: We retrospectively analyzed all adult cardiac surgical patients in 1998 for ICU stays more than 14 days. Data were analyzed to create multiple organ dysfunction scores (MODS, range 0 to 24) and hospital charges. Follow-up was conducted 1 and 2 years apart for survival and quality-of-life evaluation. RESULTS: Forty-nine patients remained in the ICU more than 14 days, comprising 3.8% of our patients but 28% of total ICU bed time. This population had a 28.5% hospital mortality, which was greater than those in the ICU less than 14 days (5.3%, p < 0.05). By 2 years, 22 of the 35 discharged patients were alive, 16 of whom had a normal quality of life. Patients alive at 2 years had lower MODS at day 14 than those who died (2.6 +/- 1.4 versus 5.5 +/- 3.8; p < 0.005) as well as lower hospital costs ($223,000 +/- $128,000 versus $306,000 +/- $128,000; p < 0.05). No patient with an MODS of at least 6 at day 14 survived. CONCLUSIONS: Patients remaining in the ICU for more than 14 days suffer a higher mortality at greater expense. A MODS at day 14 may help predict those who will not enjoy long-term survival and thus aid in the decision to terminate care.